This invention, relates generally to the assembly of printed circuit board assemblies (PCBAs) and electronic components, and more particularly to a multiple pitch tape feeder device for reliably conveying parts to a pickup location for soldering to a substrate using a pick and place assembly machine.
The present invention is a multiple pitch tape feeder device for reliably conveying parts to a pickup location for soldering or other attachment to a substrate using a pick and place assembly machine. Component carrier tape used in tape feeding equipment typically comprise a plastic or similar strip having depressions or pockets at regular intervals containing the part to be mounted on the substrate and a second, flat (e.g., Mylar) cover strip covering the depressions to retain the parts in the depressions during transport and use. This invention relates to a tape feeder device which can feed such carrier tapes in a variety of formats, including tapes which vary in pitch, i.e., different, predefined distances from one depression to the next on the tape. Most particularly, this invention relates to a variable pitch tape feeder device that is versatile and easy to operate as a result of a number of improvements incorporated therewith.
The preferred method for the automated construction of circuit boards requires the use of high speed pick and place assembly machines that pick components from a pickup location and place them at required locations on a printed circuit board for attachment. Pick and place machines rely on feeding mechanisms to reliably present the required parts to the expected pickup location. It is well-known in the industry to package small electronic parts such as integrated circuit chips in a carrier tape that is characterized by a flexible strip with depressions formed at regular intervals along its length. A part is disposed in each depression and secured by a cover strip that is adhered along its edges to the carrier tape by either a heat-sealing method or pressure sensitive adhesive. Parts that are packaged in a carrier tape require the cover strip be peeled away from the carrier tape and that the carrier tape be advanced to bring the next part to the pickup location. Normally, the carrier tape is peeled back from the carrier tape at a point just prior to the pick location as the tape is advanced in order to retain the component part in its respective pocket.
Electronic parts are packaged in carder tapes in a variety of formats, depending on the size of the part being delivered. In particular, carrier tapes are available in varying widths and pitches. The width is the distance from edge to edge perpendicular to the length of the tape. Widths common in the industry are 8 mm, 12 mm, 16 mm, 24 mm and larger. The pitch of a carrier tape is the distance from one depression (e g. lead edge) to the next (lead edge) along the length of the tape. An aspect of the present invention is directed to a tape feeder capable of delivering parts on 8 and 12 mm width tapes, though it can be easily modified to accommodate other sizes. The most popular pitches used by electronic parts manufacturers with 8 and 12 mm wide tapes are 2 mm, 4 mm, and 8 mm and 12 mm. Tapes are wound on reels and transported to the manufacturing facility. It is obvious that the part manufacturer and user will desire to use the smallest pitch tape permissible for the size of the electronic component in order to control the three-dimensional orientation of the component.
For applications requiring high speed operation using low mass components, particularly those components with pitches of 8 mm or less, it is also important to provide means to keep each part from escaping its respective recess after the cover tape strip is removed, but before it reaches the pick location. To this end, shutters have been employed to cover the carrier tape past the point where the cover strip is peeled away up to the pick location.
An example of a variable-pitch feeder is found in U.S. Pat. No. 6,032,845 for a VARIABLE PITCH TAPE FEEDER AND PITCH SELECTION SWITCH THEREFOR by Piccone et al., assigned to Hover-Davis, Inc. and hereby incorporated by reference for its teachings. A further example of a feeder is the fixed-pitch feeder shown in U.S. Pat. No. 4,327,482, where carrier tape is supplied and the cover strip is removed and is taken up by cover strip take-up reel as the carrier tape is advanced.
Tapes of varying widths are accommodated via a feeder dedicated to said specific width, whereas a variety of pitches can be accommodated by a single feeders providing a multiple-pitch feeder requires that the amount of carrier tape advance must be selectable, and the pickup location must be adjustable to assure that the component is exposed and located at the centroid of the pick location.
Heretofore, a number of patents and publications have disclosed a variable pitch tape feeder that can both vary the advance of the carrier tape and the travel distance of the shutter mechanism, the relevant portions of which may be briefly summarized as follows.
U.S. Pat. No. 5,725,140 to Weber et al. describes a variable pitch tape feeder. The feeder includes adjustment means for varying the advance of the carrier tape to accommodate tapes of varying pitch as well as an adjustment for the travel distance of the shutter mechanism.
U.S. Pat. No. 5,531,859 to Lee et al. and U.S. Pat. No. 5,294,035 to Asai et al. do not employ shutters, but enable selection of pitch advancement of a carrier tape by adjusting a pivot point in a manner similar to U.S. Pat. No. 5,725,140. For example, in U.S. Pat. No. 5,294,035, a lever is provided with a several pivot points, each one of which provides for a different travel distance of a plate which ultimately drives a feed pawl. Again, no shutter mechanism is provided and a large rectangular opening does not prevent exposed parts from escaping from their depressions.
In accordance with the present invention, there is provided a multiple-pitch tape feeder, comprising: a carrier tape reel support for supporting carrier tape having any one of several predetermined pitches and a cover tape retaining components therein; a slidable tape guide with a tape window for exposing a component at a pick location adjacent a peel edge for peeling said cover tape from the carrier tape; a path for guiding said carrier tape from a carrier tape reel to the slidable tape guide; a carrier tape drive mechanism for engaging feed-holes regularly spaced along the length of carrier tape and advancing said carrier tape through said tape guide; a pitch selection cam repositionable by an operator, said selection cam having a plurality of positions, each corresponding to one of a plurality of predetermined pitch sizes, wherein movement of said selection cam is directly translated into movement of said slidable tape guide; a sensor detecting the position of the slidable tape guide; and a control unit, responsive to said sensor, for providing a signal to said carrier tape drive means, said carrier tape drive means advancing the carrier tape a predetermined distance according to the pitch size.
The techniques described above are advantageous because they are flexible and one or more of the techniques can be adapted to any of a number of tape feeding systems. The techniques of the invention are advantageous because they provide a range of alternatives, each of which is useful in appropriate situations, that enable a single feeder to be used in an environment where multiple pitch carrier tapes are frequently usedxe2x80x94thereby increasing the usefulness of the feeder. In addition, some of the techniques described herein can be used separately in certain situations so as to achieve similar functionality. As a result of the inventions described herein, tape feeders with improved flexibility and functionality may be produced.